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Calculation of rated permissible stresses (GOST 32388-2013). Nominal permissible voltage calculator.

Each material has a set of properties that determine its further characteristics. One of these qualities is resistance to mechanical loads, which is called ultimate stress. This concept refers not only to the destruction of the material at the fracture point, but also to the appearance of residual deformation. In other words, it is resistance to external forces that lead to weakening of strength. The article talks about what such voltage is, how it is calculated and how it is determined.

General information.

Calculations of pipes and connecting parts for strength are carried out according to the nominal permissible stresses [σ]. Nominal permissible stresses [σ] are determined by the formulas: - for carbon, low-alloy, ferritic, austenitic-ferritic, martensitic steels and iron-nickel alloys

— for austenitic chromium-nickel steel, aluminum, copper and their alloys

When determining permissible stresses for low- and medium-temperature pipelines, long-term strength characteristics σ2*105/t and σ1/2*105/t In the absence of data on the conditional yield strength at 1% permanent elongation, it is permissible to use the value of the conditional yield strength at 0.2 % residual elongation σ0.2/t, it is allowed to take the safety factor for σ0.2/t equal to 1.3 instead of 1.5. Allowable stresses for titanium alloys are calculated using the formula

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where the coefficient is taken: - for titanium sheets and rolled pipes 2.6; — for titanium rods and forgings 3.0. In the absence of data on the yield strength and long-term strength, the permissible stress for aluminum, copper and their alloys is calculated using the formula

where the coefficient is taken: - for aluminum, copper and their alloys 3.5; — for aluminum casting alloys 7.0. If the permissible stress for operating conditions is determined by formula (5.4), then for pipelines made of aluminum, copper and their alloys, the permissible stress during testing is calculated using the formula

where the coefficient is taken: - for aluminum, copper and their alloys 1.8; — for aluminum casting alloys 3.5.

It is recommended to take standard values ​​in accordance with reference and scientific and technical literature.

For steel pipelines operating under creep conditions at different design temperatures, it is allowed to take as the permissible stress , calculated by the formula

where , , …, are the duration of periods of operation of the pipeline with the calculated wall temperature, respectively, , …, , h; , , ..., - nominal permissible stresses for the design service life at temperatures, respectively, , ..., , MPa; — exponent in the equations of long-term strength of steel (for alloyed heat-resistant steels it is recommended to take 8); — total design service life, hours. Permissible stresses are taken in temperature ranges of no more than 30°C. If it is necessary to determine equivalent permissible stresses for a temperature range of more than 30°C, the average value of the exponent should be used according to experimental data with a test base of no more than 0.1 of the service life, but not less than 10 hours.

For materials and structures that are not specified in this standard, reference and experimental data are used.

Group I - workshops without increased danger

  • work occurs at normal temperatures up to +5 degrees and relative air humidity up to 75% (according to the rules for the design of electrical installations (PUE);
  • floor coverings are made of non-conductive materials: tiles, wood, linoleum and similar;
  • minimum electrical installations to be grounded;
  • there are no complex metal structures;
  • there is no conductive dust in the air or on surfaces;
  • Such premises are characterized by large areas and low space fill ratio;
  • It is allowed to work with electrical devices with a voltage of 0.23 kV.

Area without increased danger for personnel

Examples: office premises, control rooms, utility rooms, computer centers, administration and management offices.

Principles for classifying premises according to the danger of electric shock.

Conductive dust settles on the wires, creates paths for blocking the wires, and the insulation is destroyed. A person with dusty hands conducts electricity better than someone with clean, dry hands.

Expert opinion

It-Technology, Electrical power and electronics specialist

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Classification of premises according to the degree of electric shock. What circumstances of the possible inclusion of a person in the circuit of electric current flow determine the choice of the maximum permissible levels of touch voltage and current through the human body. Ask, I'm in touch!

Rated permissible voltage calculators.

Initial data.

Enter the minimum tensile strength (tensile strength) value at the design temperature (G1)

Convert units of measurement online

Enter the minimum yield strength at design temperature (G2)

Convert units of measurement online

Enter the minimum proof strength (stress at which permanent elongation is 0.2%) at design temperature (G3)

Convert units of measurement online

Enter a conditional long-term strength limit for a resource of 2·100000 h at the design temperature (G4)

Convert units of measurement online

Enter a conditional tensile creep limit that causes a deformation of 1% in 2 10000 hours at the design temperature (G5)

Convert units of measurement online

Calculation for low and medium temperature pipelines.

Calculation of nominal permissible stress for carbon, low-alloy, ferritic, austenitic-ferritic, martensitic steels and iron-nickel alloys.

Result of calculation of permissible stress at design temperature (G0)

Formula for calculating the permissible stress at the design temperature:

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Calculation of nominal permissible stress for austenitic chromium-nickel steel, aluminum, copper and their alloys.

Calculation result of permissible stress at design temperature (G03)

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Formula for calculating the permissible stress at the design temperature:

Download the result of calculating the permissible stress at the design temperature:

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Calculation for high-temperature pipelines.

Calculation of nominal permissible stress for carbon, low-alloy, ferritic, austenitic-ferritic, martensitic steels and iron-nickel alloys.

Result of calculation of permissible stress at design temperature (G01)

Formula for calculating the permissible stress at the design temperature:

Download the result of calculating the permissible stress at the design temperature:

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Calculation of nominal permissible stress for austenitic chromium-nickel steel, aluminum, copper and their alloys.

Result of calculation of permissible stress at design temperature (G04)

Formula for calculating the permissible stress at the design temperature:

Download the result of calculating the permissible stress at the design temperature:

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Reference data on permissible stresses.

Data RD 10-249-98 Standards for calculating the strength of stationary boilers and steam and hot water pipelines.

Table 2.1. Nominal permissible stresses [σ] for carbon and manganese steels, independent of the design life, MPa.

, °С steel grade
St2kp St3kp St2sp, St2ps St3sp, St3ps St4ps, St4sp S3Gps 22K 14GNMA 16GNM, 16GNMA
From 20 to 50 124 133 130 140 145 150 170 180 190
150 106 115 112 125 129 134 155 179 181
200 111 100 117 121 125 147 175 176
250 80 102 86 107 111 115 140 171 172
275 102 106 109 135 170 169
300 70 98 103 130 169 167
320 126 164 165
340 122 161 163
350 120 159 161
360 157 159
370 155 157
380 152 154

Table 2.2. Nominal permissible stresses [σ] for carbon and manganese steels, MPa.

, °С steel grade
08, 10, 12K 15, 15K, 16K 20, 20K, 18K
Design life, h
10 10 2·10 3·10 10 10 2·10 10 10 2·10 3·10
1 2 3 4 5 6 7 8 9 10 11 12
From 20 to 100 — 130 — — — 140 — — 147 — —
200 — 120 — — — 130 — — 140 — —
250 — 108 — — — 120 — — 132 — —
275 — 102 — — — 113 — — 126 — —
300 — 96 — — — 106 — — 119 — —
320 — 92 — — — 101 — — 114 — —
340 — 87 — — — 96 — — 109 — —
350 — 85 — — — 93 — — 106 — —
360 — 82 — 82 — 90 — — 103 — 103
380 — 76 76 71 — 85 85 — 97 97 88
400 73 73 66 60 80 80 72 92 92 78 71
410 70 68 61 55 77 72 65 89 86 70 63
420 68 62 57 50 74 66 58 86 79 63 56
430 66 57 51 45 71 60 52 83 72 57 50
440 63 51 45 40 68 53 45 80 66 50 44
450 61 46 38 35 65 47 38 77 59 46 39
460 58 40 33 29 62 40 33 74 52 38 34
470 52 34 28 24 54 34 28 64 46 32 28
480 45 28 22 18 46 28 22 56 39 27 24
490 39 24 40 24 49 33
500 33 20 34 20 41 26
510 26 35

Continuation of Table 2.2

, °С steel grade
16GS, 09G2S 10G2S1, 17GS, 17G1S, 17G1SU 15GS
Design life, h
10 10 2·10 10 10 2·10 10 10 2·10
1 2 3 4 5 6 7 8 9 10
From 20 to 100 — 170 — — 177 — — 185 —
200 — 150 — — 165 — — 169 —
250 — 145 — — 156 — — 165 —
275 — 140 — — 150 — — 161 —
300 — 133 — — 144 — — 153 —
320 — 127 — — 139 — — 145 —
340 — 122 — — 133 — — 137 —
350 — 120 — — 131 — — 133 —
360 — 117 — — 127 — — 129 —
380 — 112 112 — 121 121 — 121 121
400 107 107 95 113 113 96 113 113 96
410 104 97 83 107 102 85 107 102 85
420 102 87 73 102 90 75 102 90 75
430 98 76 63 97 78 65 97 78 65
440 95 68 55 92 70 55 92 70 55
450 89 62 46 88 63 46 88 63 46
460 83 54 38 82 54 38 82 54 38
470 71 46 32 71 46 32 71 46 32
480 60 60 60
490

Notes: 1. Above the line are the stress values ​​determined by the yield strength depending on temperature.

2. The values ​​of permissible stresses in the columns for a resource of 10 and 2·10 hours, marked above with the sign “-“, are taken equal to the corresponding values ​​in the column for a resource of 10 hours.

3. The values ​​of permissible stresses indicated below correspond to the operation of elements under creep conditions and are determined by the long-term strength limit for the corresponding resource.

Table 2.3. Nominal permissible stresses [σ] for heat-resistant steel, MPa.

, °С steel grade
12ХМ, 12МХ 15ХМ
Design life, h
10 10 2·10 3·10 10 10 2·10 3·10
1 2 3 4 5 6 7 8 9
From 20 to 150 — 147 — — — 153 — —
250 — 145 — — — 152 — —
300 — 141 — — — 147 — —
350 — 137 — — — 140 — —
400 — 132 — — — 133 — —
420 — 129 — — — 131 — —
440 — 126 — — — 128 — —
450 — 125 — — — 127 — —
460 — 123 123 123 — 125 125 125
480 120 120 102 102 122 122 113 103
500 116 95 77 64 119 105 85 76
510 114 78 60 53 117 85 72 62
520 107 66 49 43 110 70 58 50
530 93 54 40 35 97 56 44 39
540 77 43 80 45 35 31
550 60 62 35 26 23
560 52 27
570 42 21
580
590
600
610
620

Continuation of Table 2.3

, °С steel grade
12Х1МФ 12X2MFSR 15Х1 М1Ф
Design life, h
10 10 2·10 3·10 10 10 2·10 10 10 2·10 3·10
1 2 3 4 5 6 7 8 9 10 11 12
From 20 to 150 — 173 — — — 167 — — 192 — —
250 — 166 — — — 160 — — 186 — —
300 — 159 — — — 153 — — 180 — —
350 — 152 — — — 147 — — 172 — —
400 — 145 — — — 140 — — 162 — —
420 — 142 — — — 137 — — 158 — —
440 — 139 — — — 134 — — 154 — —
450 — 138 — 138 — 133 — — 152 — —
460 — 136 136 130 — 131 131 — 150 150 150
480 133 133 120 107 128 128 119 146 145 130 123
500 130 113 96 88 121 106 97 140 120 108 100
510 120 101 86 79 115 94 87 137 107 96 90
520 112 90 77 72 105 85 79 125 96 86 80
530 100 81 69 65 95 78 70 111 86 77 72
540 88 73 62 58 87 70 63 100 78 69 65
550 80 66 56 52 80 63 56 90 71 63 58
560 72 59 50 46 72 57 50 81 64 57 52
570 65 53 44 41 65 52 45 73 57 51 47
580 59 47 39 36 59 46 41 66 52 46 43
590 53 41 35 32 53 41 36 60 47 42 39
600 47 37 31 29 47 37 33 54 43 38 35
610 41 33 41 33 28 48 40
620 35 35 43

Notes: 1. Above the line are the stress values ​​determined by the yield strength depending on temperature.

2. The values ​​of permissible stresses in the columns for a resource of 10, 2·10 and 3·10 hours, marked above with the sign “-“, are taken equal to the corresponding values ​​in the column for a resource of 10 hours.

3. The values ​​of permissible stresses indicated below correspond to the operation of elements under creep conditions and are determined by the long-term strength limit for the corresponding resource.

Table 2.4. Nominal permissible stresses [σ] for high-chromium and austenitic steels, MPa.

, °С steel grade
12Х11В2МФ 12Х18Н12Т; 12Х18Н10Т 09Х14Н19В2БР, 09Х16Н14В2БР, 10Х16Н16В2МБР
Design life, h
10 10 2·10 10 10 2·10 3·10 10 10 2·10
1 2 3 4 5 6 7 8 9 10 11
From 20 to 150 — 195 — — 147 — — — 147 —
250 — 183 — — 125 — — — 131 —
300 — 175 — — 120 — — — 128 —
350 — 167 — — 116 — — — 125 —
400 — 158 — — 111 — — — 123 —
450 — 152 — — 107 — — — 120 —
500 145 145 145 — 104 — — — 117 —
520 143 134 128 — 103 — — — 116 —
530 141 124 119 — 103 — 102 — 116 —
540 140 115 108 — 102 102 100 — 115 —
550 130 107 100 — 102 100 93 — 115 —
560 121 97 90 101 101 91 87 — 114 —
570 113 87 80 101 97 87 81 — 114 —
580 104 78 72 100 90 81 74 — 113 113
590 95 69 64 98 81 73 68 — 113 109
600 87 60 55 94 74 66 62 112 112 102
610 78 51 47 88 68 59 55 111 104 94
620 70 47 39 82 62 53 50 111 97 87
630 62 37 31 78 57 49 46 110 89 79
640 54 27 23 72 52 45 42 110 81 72
650 45 20 65 48 41 38 109 74 64
660 38 60 45 37 103 66 56
670 30 55 41 34 96 59 49
680 50 38 32 88 52 41
690 45 34 28 79 44 34
700 40 30 25 71 37 27

Notes: 1. Above the line are the stress values ​​determined by the yield strength depending on temperature.

2. The values ​​of permissible stresses in the columns for a resource of 10, 2·10 and 3·10 hours, marked above with the sign “-“, are taken equal to the corresponding values ​​in the column for a resource of 10 hours.

3. The values ​​of permissible stresses indicated below correspond to the operation of elements under creep conditions and are determined by the long-term strength limit for the corresponding resource.

Table 2.5. Recommended. Nominal permissible stresses [σ] for steel 10Х9МФБ, MPa.

, °С Design life, h
10 10 2·10
1 2 3 4
From 20 to 150 — 167 —
250 — 160 —
300 — 157 —
350 — 154 —
400 — 151 —
450 — 148 —
470 — 147 147
480 146 146 143
490 145 138 132
500 145 127 122
520 127 108 102
540 109 90 83
550 100
560
570
580 78
590 71 58 53
600 52*
610 62* 50*
620 60* 48*
630 57* 45*
640 55* 43*
650 52* 41*

Notes: 1. Above the line are the values ​​of permissible stresses determined by the yield strength depending on temperature.

2. The values ​​of permissible stresses in the columns for a resource of 10 and 2·10 hours, marked above with the sign “-“, are taken equal to the corresponding values ​​in the column for a resource of 10 hours.

3. The values ​​of permissible stresses indicated below correspond to the operation of elements under creep conditions and are determined by the long-term strength limit for the corresponding resource.

4. The values ​​of permissible stresses with the * sign were obtained by extrapolation from short-term test bases and must be adjusted taking into account the requirements of subsection 2.1. For intermediate values ​​of the service life indicated in the tables, the value of the permissible stress can be determined by linear interpolation of the nearest values ​​between resources, rounded down to 0.5 MPa, if the difference between these values ​​does not exceed 20% of their average value. In other cases, “logarithmic” interpolation should be used. Extrapolation of permissible stress values ​​for a resource of less than 10 is not permitted without agreement with specialized research organizations. Permissible stresses for foreign steel grades approved for use by the State Mining and Technical Supervision Authority of Russia must be established by specialized research organizations. For steel 2.1/4 Cr1Mo (10CrMo910 for pipes according to DIN 17175 and for sheets according to DIN 17155), the permissible stress values ​​given in Table 2.6 can be used.

Table 2.6. Nominal permissible stresses for steel 2.1/4 Cr1Mo (10CrMo910) for a design life of 10 hours.

, °С [], MPa
20-100 180
200 163
250 160
300 153
350 146
400 140
450 133
480 123
500 96
520 73
540 53
560 38
580 28

2.3. For steel grades not listed in Tables 2.1-2.4, and for other metals approved for use by Gosgortekhnadzor of Russia, the nominal permissible stress should be taken equal to the lowest of the values ​​given in Table 2.7, obtained by dividing the corresponding calculated characteristic of the tensile strength of the metal for the appropriate safety margin for this characteristic.

Group II - premises with increased danger

  • The production temperature is above 30 degrees (According to the PUE).
  • The material used to make floor coverings is usually conductive: earth, reinforced concrete, metal alloys. Provided there is moisture on the surface.
  • High air humidity (more than 75%).
  • For such premises, fluctuations in humidity (up to a state of saturation) or the release of steam are allowed.
  • There are accumulations of conductive dust in the room: on the walls, floors, cables, equipment.
  • The area fill factor is more than 20%.

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The attic is a room with an increased risk of electric shock.

If one of the listed factors is present, the premises are classified as group 2 (according to the PUE).

Examples: vehicle service areas, unheated attics and basements, welding and thermal work rooms, repair shops, coal mills, etc.

Categories of premises according to the degree of danger of electric shock according to the PUE

1.3 Balanced people, with a healthy heart and nervous system, a dry, clean body, and also in a sober state, have greater resistance to current.

Expert opinion

It-Technology, Electrical power and electronics specialist

Ask questions to the “Specialist for modernization of energy generation systems”

Categories of premises according to the degree of danger of electric shock 3 Balanced people, with a healthy heart and nervous system, a dry, clean body, and also in a sober state have greater resistance to current. Ask, I'm in touch!

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